There are a lot of such shenanigans going on, people who blatantly flout the rules by not even bothering to stay for a day are just the minority of dumb ones.
Many more reside in grey areas - for e.g. many PMEs who buy a BTO but only stay there during the weekends as they stay with parents 5 out of 7 days. If you minus them being frequently abroad for holidays, these people likely only stayed in their BTO for less than a quarter of the time.
When their parents pass on, they simply inherit the flat they are staying at in name and then sell off the BTO for a handsome profit.
This is not new.
If a family of 5 children. All children buy flats somehow but stay with their parents.
But they play with the resale markets after MOP completed.
I recently waited for 5 years to get the BTO. At the time of key collection, i was asked to submit my wife's income as they said they feel our combined income may be higher. This is the third time asking for such documents as I have submitted all the income documents duly twice.
Since I could not submit the documents on the third time immediately, I appeal to defer the key collection date at a later date. However, HDB cancelled my BTO application and slapped a penally of about $20000/-. This is how HDB plays the game to drive their ROI
HDB officers were so rude and arrogant as they do not care when locals asked for any help. Typical mentality of PAP government., I have decided rather live in a Good Class Bungalow House than living in a HDB. All those responsible for the ill treatment will be held responsible for evil works in due time.